Previous rotary expander devices of the gerotor type or the Wankel trochoidal rotor type have required working members and working chambers having shapes which are expensive and difficult to fabricate. There is, therefore, a need for a fluid pressure device having simple shapes of working member and working chamber which are easily and economically fabricated.
Worn members on previous devices have caused increased clearances and excessive leakage causing deterioration of efficiency and have required replacement with new parts. There is therefore a need for a fluid pressure device which is designed in a manner which enables adjustment of the clearances between working member and working chamber thus enabling easy fitting at assembly and take up of wear at repair.
The present invention is a rotary expander device which employs a diagonally split square flat sided working chamber which can be adjusted by shim means to fit a sext-arcuate working member with flat sides and arcuate periphery. The six arcuate surfaces of the rotor periphery are true arcs with radii centered on vertices of an equilateral triangle. The flat sides of the chamber form a true square in which the three lobed rotor revolves, with the chamber width adjustable by shim means to fit the width of the rotor.
In the present invention, as the three lobed rotor revolves in the square chamber it makes sliding contact with all four sides simultaneously and the geometry of these parts causes the center of the rotor to describe a circular obit around the center of the square chamber. The orbit is retrograde to the direction of rotation of the rotor and deviates slightly from a true circle. The orbital velocity is three times the rotor velocity and is usefully employed as a novel feature of the invention. Orbiting of the rotors of the previous art required auxiliary mechanisms, while the orbiting of the rotor of the present invention is automatically provided by the geometry.